A typical method for diagnosing actuators diagnoses actuators by equipping a holding sensor in a power line connected between a battery and an actuator controller and using an external diagnostic terminal connected to the actuator controller. An inspector manually manipulates the actuators at a driver's seat depending on instructions of the diagnostic terminal and may diagnose the actuators by a method for indirectly measuring power consumption by the holding sensor at the manipulation instant and determining normality/failure of the actuators by receiving and confirming the measured current through the terminal. Therefore, a diagnosis time is delayed due to a separation time of the holding sensor after the diagnosis and measurement errors occur due to an indirect measurement of power consumption, thereby causing misjudgment at the time of the diagnosis. Further, the method causes the measurement errors depending on attachment schemes (position, angle, proximity, and the like of a sensor) for attaching a holding sensor to a battery line by an inspector.
Among the typical methods for diagnosing actuators, there is a method for measuring power at the time of separating the actuators and for measuring power at the time of mounting the actuators, detecting a change of power at this time, and comparing the detected change of power with a reference power value to perform a decision on a failure of the actuators. In this case, when the measurement result is out of a normal decision range, since the actuators need to be mounted again and are diagnosed and then separated, much time and many efforts may be required to diagnose the actuator. Further, a delay due to detachment and attachment of external inspection equipment and the actuators in a vehicle process line which needs to test many vehicles within a limited release time may lead to a reduction of productivity.